Don't try to do all at once;take one ____a time.A at Bon Cin Dfor
问题描述：
Don't try to do all at once;take one ____a time.A at Bon Cin Dfor
答
Don't try to do all at once;take one at a time.
at a time是"每次"的意思
in a time是"一段时间后"的意思
on a time是"在一段时间里"的意思
for a time是"一段时间"的意思